Mlusby, thanks for the experiment, I have been thinking about this issue for a while. I wonder what the difference would have been if you would have left the 3oz batch in for 8 days, so that the hops would have all been in contact for the same amount of time?
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user3366Apr 24 '13 at 2:32

If people are interested in introducing extra oxidation and stale flavors to the beer then I'd say its the best way to go. I agree with Denny. To much of a hassle with little reward.
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brewchezApr 12 '11 at 17:52

Can you please provide some evidence/sources?
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markusApr 9 '13 at 20:42

My own experimentation and experience is what I go by.
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Denny Conn♦Apr 11 '13 at 4:00

A lot of brewers that make excellent dry-hopped beers have a limit to how many days they leave their beers on the dry hops. For example, this presentation on IIPA's by home brewer Nathan Smith (PDF), says that Firestone Walker only uses dry hops for 5 days, and Smith suggests a maximum contact time of 7 days. And Smith summarizes the purpose of multiple small dry-hop additions as giving the beer "bigger, longer-lasting aroma".

The thing to keep in mind here is that these brewers are using conicals and can pull the hops out of the beer using the bottom valve in the conical, preventing oxidation problems. If you're not using a conical, it's going to be a bit trickier to do multiple small dry-hop additions and avoid oxidation. My approach would be to dry hop in a keg. Store the dry hops in hop bags and suspend the bags from the lid using fishing line or something similar. Fill the keg headspace with CO2, leave the hops in the beer for 5-7 days, pull the bag and then repeat the process as many times as you like.

Will it make a big difference vs. just doing one hop addition? That's for you to decide, it's your beer. Try it both ways and see what you prefer.

Okay, here's the deal: I believe that time is the predominant factor in dry hopping, and I had previously thought quantity was just as important.

I did an IPA with Rye, double dry hopping, divided into:

1.5 ounces of hops for 4 days, 1.5 ounces of hops for 4 days

3 ounces of hops for 4 days.

Though I did not expect a difference, and with the help of a friend who is very good at distinguishing differences, we determined the first batch was significantly more aromatic. This is somewhat noticeable in the smell, but also very pronounced in your sinuses, a great addition to a beer I'm now quite proud of.

This seems to validate that a significant amount of your aroma comes from time in contact with hops, more so than quantity of the hops. Therefore, I would guess multiple additions is the best way to get the most aroma, once you're worried about leaving the hops in longer than x days (many people differ on how long it takes to get unpleasant taste from too much time in contact with hops).

Vinnie Cilurzo does (did) it, for whatever that's worth. From that article, it sounds as though the point is to keep a "big", fresh hop aroma, while removing most of the "bits" before they can contribute significant off flavors/aromas.

I haven't heard of anyone actually doing this, but I imagine the rationale is that dry hopping for longer than 5 days or so can lead to "stemmy" or grassy flavors. I guess if you were trying to go way overboard on the dry hopping you could get a little extra aroma without the stemmy/grassy flavors.

That said, no need to do this. Using the appropriate amount of dry hops just once should always do the trick.